Integrated Hydrological and Hydrochemical Analysis of Arsenic and Iron Behavior in Waters of a Decommissioned Tin Mine in Ehrenfriedersdorf, Germany

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

I have thoroughly reviewed your and have some suggestions for improvement.

Abstract:

Please include specific details about the sample size, locations, and the methodology used for sample collection in the abstract. Also, elaborate on the procedure employed for analyzing the Climatic Water Balance (CWB).

Introduction:

Consider reorganizing the sections for better flow. I recommend moving section 1.2 to the Methods section, placing section 1.3 at the end of the Introduction, and positioning section 1.4 in the second last paragraph of the Introduction. This will enhance the coherence of your narrative.

Methods:

Provide additional information about the underlying geology and changes in land use/land cover within the study area. Adding these details will strengthen the foundation of your study and improve the clarity of your methods. Improve the quality of figures.

Discussion:

Enhance your discussion by comparing and contrasting your findings with international research. Incorporating relevant literature can provide a broader perspective and add value to your research outcomes. For international references, consider exploring works such as

Qaiser, F. U. R., Zhang, F., Pant, R. R., Zeng, C., Khan, N. G., & Wang, G. (2023). Characterization and health risk assessment of arsenic in natural waters of the Indus River Basin, Pakistan. Science of The Total Environment, 857, 159408.

Shammi, M., Rahman, M.M., Bondad, S.E., Bodrud-Doza, M., 2019. Impacts of salinity intrusion in community health: a review of experiences on drinking water sodium from coastal areas of Bangladesh. Healthcare. MDPI, p. 50.

Smedley, P.L., Kinniburgh, D.G., 2002. A review of the source, behaviour and distribution of arsenic in natural waters. Appl. Geochem. 17, 517–568.

Thank You.

Comments on the Quality of English Language

Enhance the English language of the manuscript

Author Response

Dear Reviewer,
thank you for your suggestions.

I have rewritten the abstract to oblige your recommendations.

Likewise, I have restructured the Introduction.

Methods: I have add information regarding the land use at the tailing ponds.
The cited literature from Hösel, 1994 encompasses very detailed geological study of the mine site.

Some more text reagarding geology has been added as well as a map of a general geological and geographical setting.

We have managed to improve and simplify the charts.


I have added the recommended references into the manuscript. I'm not able the combine the exisiting References with the new ones I added while improving the manuscript. I'm using Citavi software and it seems that is not possible to merge exisiting reference feld functions. I'm apologizing for the incovenience and the additional editorial work. The newly added references are in the form of (Surname, YYYY) for easier identification.


Regarding English: Our PhD student from Canada had a detailed look at the manuscript and executed only minor changes (may be displayed blue if the "track changes" option is activated). He found the manuscript well-written. We have corrected wrongly used mining terminology as well as German abbreviations.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is well written but lacks presentation of the claimed data. I have mentioned some comments in the attached manuscript. Please address the comments.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

thank you for your comments.

I have adjusted the sentence that you found problematic.

Regarding the display of data: I have not included tables or figures on purpose. My goal was to generally describe the mine subfields regarding overall chemistry. However, including the figures displaying the courses of other metals would overfill the paper with figures - which I wanted to avoid. The paper should focus on Arsenic and Iron behavior.
If a reader is interested to obtain these, I can disclose them.


If you, however find those figures indispensable, I'll add them to the manuscript.

Kind regards,
Viktoria

Reviewer 3 Report

Comments and Suggestions for Authors

1.    Consider adding a geologic map or cross section to illustrate geologic setting

2.     Line 44. Consider adding an equation showing the oxidation of arsenopyrite to supplement the discussion.

3.     Line 145 Consider rewriting the objective and change it from establishing monitoring to understanding the geochemical and hydrologic controls on the system.

4.     Figures two (2) to seven (7) and nine present a lot of time series data. Consider statistical analysis of data and whether you can define lag period more precisely and degree of correlation between flow, weather model and chemistry. This could strengthen the observations made from visual inspection of the graphs.

5.     Could the storage volume of water change in the minepool as precipitation changes? This could affect the discharge rate. Storage change is not discussed so I am asking if it was considered.

6.     Line 443 mentions oxidation of Fe and As. Does the reported pH and Eh data indicate that oxidation of either or both is feasible?

7.     If chemical analysis included major cations and anions as well as metals, then it should be possible to speciate the solutions and calculate mineral saturation indices for arsenopyrite, pyrite and other minerals in the system. Using PHREEQC or similar software. These types of calculations could strengthen and support the discussion of behavior of elements such as Fe or As.

8.     The conclusions section is rather brief. Is there anything further that can be stated about the results of the study?

Author Response

Dear Reviewer,
thank you for your valuable questions, they made me think a lot.

I have added a general geographical and geological map of the area including mine plan for reader's better idea..

Points 2) and 3) will be executed.

4) Very good point.
However, the amount of chemical data is not sufficient for such analysis.
I could only do such analysis compairing the daily CWB and daily outflows at the TSS portal because the daily data are available. If we consider what we already know - that TSS portal outflow does not only react to CWB changes (due to the coupled external water inflows), the relevancy of such statistical analysis would be quite low.
Anyway, I'm very thankfull for your remarks and will keep statistical analysis in mind in future scenarios wher more data will be available.

5) Another valid question. There was no hydrological research conducted at this site except of ours and a small thesis in 2008. The fact is that we can only assume that the storage is quasi-stationary because the water level of the flooded mine body does not show measurable changes.

6) The pH in the Rigole 28 is around 6.7 and the Eh moves between 250-350 mV. Using Pourbaix diagramm, we end up at the border between H2AsO4- and HAsO42- for Arsenic and Fe2O3 for Iron.

7) I have indeed conducted such calculations, however with a different intention.
In the case of Rigole 28, PHREEQC did not suggest prevalence of As3+ species so that I can't rely fully on the calculated speciations.

Regarding the saturation indices: It does not make a sense to have a look at the crystalline phases such as pyrite and arsenopyrite. Moreover, we must see the relevant amorphous phases - Fe(OH)3, FeS (ppt), MS etc.
I have added a few paragraphs discussing first the challenges in sulfide determination in the results section and then a paragraph about SI in the discussion section.

8) I will extend the conclusion of our manuscript.


Have a great day,
Viktoria

Reviewer 4 Report

Comments and Suggestions for Authors

Inaugural Evaluation

The integrated hydrological analysis of arsenic and iron behavior in a decommissioned tin mine seeks to understand the complex interaction between geological, hydrogeological and chemical factors affecting contaminant fate and transport. Geological and hydrogeological mapping reveals complex underlying formations, aquifer features, and groundwater flow routes. Subsequent water and soil sampling over the mine helps collect data for chemical analysis. Arsenic and iron concentrations are quantified using advanced laboratory methods to reveal their spatial distribution and chemical forms. Hydrological modeling, including groundwater flow and pollutant transport simulations, predicts migration pathways and temporal fluctuations. Risk assessments determine the possible impact on human health and the ecology, directing remedial measures. Integrating data into a thorough technical report provides a solid scientific framework for decision-making to reduce arsenic and iron contamination in the decommissioned tin mine.

The presence of arsenic in the environment and its impact on human health are major concerns, particularly due to the contribution of mining activities to its widespread dispersion. The authors examines the future of arsenic and iron in an abandoned tin mine located in Ehrenfriedersdorf, Germany. Although historic mining sites sometimes lack sufficient data, they conducted a thorough investigation into the intricate relationship between climate conditions, hydrological processes, and the behavior of arsenic in mine streams. This involved thoroughly studying the site, monitoring activities, and analyzing local weather data. The investigation uncovers discernible patterns in the levels of arsenic at different points within the mine system, providing insights about possible water seepage and external factors affecting it. Their research highlights the significance of continuous surveillance and comprehensive water management techniques to reduce the potential hazards of arsenic pollution in comparable mining settings. In addition, examining climatic water balances offers valuable information about the mine's hydrological patterns, shedding light on how precipitation and potential evapotranspiration affect arsenic levels. This knowledge can greatly enhance water management strategies.

 Recommendations/ Questions

I believe this work will make a significant contribution to the field and has tremendous potential. However, I have only minor recommendations after carefully reviewing the manuscript.

The first paragraph should have a reference. here is a recommendation: https://doi.org/10.12991/mpj.2018.59

Owing to arsenic toxicity: Assessment of Arsenic Levels in Human Hair by Hydride Generation Atomic Absorption Spectrometry: A Toxicological Application, Atomic Spectroscopy, 2010; 31(1):1-5

I believe that general ecotoxicological health risk should also be mentioned in the following paper: https://doi.org/10.1007/s11356-022-23937-2

The data obtained from this research can be processed for health risk assessment as well as statistical tools like principal component analysis, or EPA PMF, can be employed to provide a scientific evidence of the origins of arsenic and iron.

Decision

 The issue being investigated is quite engaging, and the research process used has a thorough and rigorous framework. A comprehensive explanation was provided about the fundamental components and methodologies used in the research. The paper is considered acceptable after minor modifications.

Author Response

Dear Reviewer,
thank you for your comments.

I am, unfortunately, not able to acces the first recommended reference - the link redirects me to this webpage https://cnrl-careers.com/?id=585 and I am not able to see the recommended paper.

Regarding the second recommended reference - I tried to search whether there was a similar research conducted in our area but it does not seem to exist. In that case I could compare the As levels of the people living in our area with those mentioned in the recommended paper!

I may add the third recommended reference to the manuscript.


Have a great day,
Viktoria